Malaysia Airlines Flight 370 went down in the southern Indian Ocean, Malaysian Prime Minister Najib Razak said Monday, citing a new analysis of satellite data by a British satellite company and accident investigators.

A relative of a missing passenger briefed by the airline in Beijing said, "They have told us all lives are lost."

While the announcement appeared to end hopes of finding survivors more than two weeks after the flight vanished, it left many key questions unanswered, including what went wrong aboard the Beijing-bound airliner and the location of its wreckage in the deep, wild waters of the Indian Ocean.

Their conclusion appears to be based upon satellite data analysis, leaving the families in a state of deep grief and lingering uncertainty:

Sarah Bajc, the partner of the only American aboard the flight, Philip Wood, canceled all media interviews after the announcement.

"I need closure to be certain, but cannot keep on with public efforts against all odds," she wrote. "I still feel his presence, so perhaps it was his soul all along."

While investigators have yet to find even a piece of the plane, the Prime Minister based his announcement on what he described as unprecedented analysis of satellite data by British satellite provider Inmarsat and the British Air Accidents Investigation Branch. He didn't describe the nature of the analysis.

But he said the data -- drawn from satellite pings the ill-fated airliner continued to send throughout its final flight -- made it clear that the plane's last position was in the middle of the remote southern Indian Ocean, "far from any possible landing sites."